Another option would be to use one of the BES hosting services, do a search in these forums for some links. Though in the long run the cost of 'leasing' that kind of service from another organization would probably outweigh the cost of deploying your own BES.

Also consider how much administration/configuration time you or other staff have available. Once things are up and running the BES is fairly straightforward, but the initial learning curve can be steep for new administrators.